Over the years, railway boxcars and freight cars have progressed from relatively simple general purpose wooden structures mounted on flat cars to more elaborate arrangements including insulated walls, refrigeration equipment, nailable metal floors, and other features for specific applications. Various types of railway boxcars and freight cars are presently manufactured and used. A typical railway freight car includes an enclosed structure mounted on a railway car underframe. The enclosed structure may include an outer shell and interior paneling. For some freight cars, such as refrigerated box cars, one or more layers of insulation may be disposed between the outer shell and the interior paneling.
The outer shell of a railway freight car often has an exterior surface formed from various types of metal such as steel or aluminum alloys. The interior paneling is often formed from wood and/or metal as desired for the specific application. Sliding doors are generally provided on each side of the enclosed structure for loading and unloading freight. Conventional railway freight cars may be assembled from various pieces of wood, steel and/or sheets of composite material such as fiberglass reinforced plastic and generally require significant amounts of raw material, labor and time to complete manufacture and assembly of each freight car.
The underframe for many railway freight cars includes a center sill with a pair of end sills and a pair of side sills arranged in a rectangular configuration corresponding approximately with the dimensions for the floor of the freight car. Cross bearers and cross ties are often provided to establish the desired rigidity and strength for transmission of vertical loads to the center sill. A plurality of longitudinal stringers are typically provided on each side of the center sill to support the floor of the enclosed structure. Examples of such railway car underframes are shown in U.S. Pat. Nos. 2,783,718 and 3,266,441. Both of these patents are incorporated by reference for all purposes within this application.
For many years various techniques have been used to provide nailable steel floors for railway freight cars. The Association of American Railroads (AAR) Mechanical Division Manual of Standards and Recommended Practices, Specification M-964-92 provides information concerning the manufacture and testing of such nailable steel floors. U.S. Pat. No. 4,224,880 entitled "Railway Car Nailable Floor" provides additional information concerning such floors. This patent is incorporated by reference for all purposes within this application.
Various types of load dividers and freight securing systems have previously been used to prevent undesired movement of freight contained within an enclosed structure of a railway freight car. The use of such systems is particularly important when the freight car is only partially loaded. Examples of such systems are shown in U.S. Pat. No. 5,370,482 entitled "Cargo Securement System" and U.S. Pat. No. 5,386,674 entitled "Two Piece Bulkhead Door for Rail Cars and the Like." The above patents are incorporated by reference for all purposes within this application.
Nailable metal floors provide advantages over wooden floors. A typical nailable metal floor structure may include multiple floor panels. However, the floor panels are typically comprised of several nested metal planks. This results in complex construction of the floor panels and a series of grooves in each floor panel. Also, an additional metal strip must be applied across each end of the panel to "finish" the panel ends.